The power output of a gas turbine engine is proportional to the mass flow rate of the compressed airflow leaving the compressor. The compressor has a fixed capacity for handling a volumetric flow rate of the airflow at a given rotational speed. The mass flow rate of the airflow decreases with an increase in ambient temperatures because the density of the air decreases as the temperature increases. The efficiency and power output of the gas turbine engine thus decreases with increases in ambient temperatures.
One of the known techniques to augment power output includes reducing the temperature of the inlet airflow. A power augmentation system may include a chiller coil and/or an evaporative cooler so as to reduce the temperature of the incoming airflow. The use of a power augmentation system, however, may add resistance to the airflow entering the compressor. This resistance may be defined as a pressure drop in the inlet air system. Turbine efficiency and power output also are a function of the inlet system pressure drop. The higher the inlet system pressure drop, the lower the efficiency and overall power output of the turbine. Moreover, adding a power augmentation system to existing gas turbines generally involves considerable downtime for such an extensive retrofit.
Other causes of higher inlet system pressure drops include caking of the inlet filters during highly humid ambient conditions as well as during fogging conditions. Inlet air heating may be used so as to reduce the humidity ratio of the inlet air during those conditions. As above, however, raising the inlet air temperature generally leads to a reduction in power generation capacity, especially at base load conditions. Also, when the inlet chilling/heating coils are located upstream of the air filter elements to reduce cost and eliminate the need for gas turbine downtime, caking may develop on the filter elements during the inlet air chilling operation when the water is condensed and inlet air humidity ratio approaches one hundred percent (100%). To avoid such caking, which may lead to a higher inlet pressure drop and gas turbine shutdown, the inlet air chilling/heating coils generally are installed downstream of the final filters.
There is thus a desire for an improved inlet air chilling system. Such an improved inlet air chilling system may provide for both inlet air temperature and humidity control and, hence, avoid caking and the like while providing overall increased efficiency and power output. Moreover, such an improved system may be a retrofit without the need for extensive downtime and expense.